Inflatable folding wings for a very high altitude aircraft

ABSTRACT

A foldable wing for use with a very high altitude aircraft capable of operating at an altitude at or above 85,000 feet is disclosed. The foldable wing may employ a spiral fold deployment, wherein a hinge between each segment of the foldable wing is slightly offset from the perpendicular. Successively positioned wing segments fold over one another. Alternatively, the hinges are substantially perpendicular so that each respective wing segment folds linearly against the next wing segment. An inflatable rib, with inflatable arms, can be inflated to provide a force against two adjacent arms, thereby deploying the wing segments through a full 180° of rotation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 12/358,036, filed Jan. 22, 2009, which claims priority to U.S. Patent Application No. 61/023,075, filed Jan. 23, 2008, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a wing structure for aircraft. More particularly, the invention relates to an apparatus, and method for its use, of a folding wing structure for a very high altitude aircraft. This particular invention combines both inflatable and rigid hinged elements.

2. Background Art

For aircraft that operate at very high altitudes, the wing structure is a very important criterion. Very high altitudes means altitudes between about 85,000 feet and about 150,000 feet above sea level (ASL). At these altitudes, air densities are very low, and therefore generally, wing structures need to be relatively large areas compared to a similarly sized aircraft operating at lower altitudes of, for example, about 35,000 to 45,000 feet ASL, in order to generate the lift necessary to functionally fly.

Furthermore, if an aircraft is developed to operate at such altitudes, it is desirable to allot as much weight as possible to payload (e.g., sensors, and things of that nature), and to minimize unnecessary weight expenditures wherever possible. As a result, the use of composite materials has recently increased. If the wings could be made of composite and/or inflatable materials, yet still provide the wing area and lift necessary to properly operate at the desired high altitudes, an enormous operating benefit can be obtained.

Because of recent historical developments, a need has been developed to place unmanned aerial vehicles to locations literally around the ground within several hours notice. One manner of deployment can be via rockets, launched from ground locations and/or ocean-going ships. In these cases, the aircraft would have to be foldable and be able to quickly begin operating at high altitudes upon deployment from the rocket.

Thus, a need exists to develop a foldable aircraft, with foldable inflatable wings that can operate at very high altitudes.

SUMMARY OF THE INVENTION

It is therefore a general aspect of the invention to provide a very high altitude foldable inflatable aircraft that will obviate or minimize problems of the type previously described.

According to a first aspect of the present invention, a foldable aircraft is provided comprising an inflatable rib for use in a wing of a very high altitude aircraft capable of operating at an altitude at or above 85,000 feet, the inflatable rib comprising: a plurality of tubes including an innermost tube; a plurality of outer connecting surfaces, wherein the outer connecting surface connects one of the plurality of tunes to an adjacent one of the plurality of tubes; an innermost connecting surface that connects an inner perimeter of the innermost tune to itself; and a linking tube that is connected to each of the plurality of tubes, and is configured to receive gas and to distribute the received gas to the plurality of tubes, thereby inflating each of the tubes to form the inflatable rib.

The gas may comprise a high pressure gas having a pressure at or above 10 pounds per square inch (psi). The gas may be generated by a pressure tank, a chemical reaction gas generator, or a propulsion system associated with the very high altitude aircraft. Each of the plurality tubes may be substantially cylindrical.

According to a second aspect, an inflatable rib for use in a wing of a very high altitude aircraft capable of operating at an altitude at or above 85,000 feet, is provided, the inflatable rib comprising: a single inflatable structure substantially configured to function as a wing rib, and configured to receive a high pressure gas generated by an external gas generating source, wherein the high pressure gas has a pressure at or above 10 psi. The external gas generating source may comprise a pressure tank, a chemical reaction gas generator, or a propulsion system associated with the very high altitude aircraft.

According to a third aspect, a wing segment is provided comprising at least two inflatable ribs, wherein a wing flexible skin between the ribs is supported by and maintained in a predetermined airfoil shape by a series of stringers and a trailing edge. At least one of the stringers and/or the trailing edge may comprise an inflatable tube. Alternatively, at least one of the stringers and/or the trailing edge may comprise a rigid shape made from a metal and/or one or more composite materials. Each of the stringers may comprise one or more rigid materials on an exterior of the wing segment and an inflatable tube inside the wing segment, wherein the inflatable tube is configured to provide stiffness with a predetermined stowed volume and to provide a predetermined wing segment shape.

According to a fourth aspect, a foldable wing structure for use in a very high altitude aircraft capable of operating at an altitude at or above 85,000 feet is provided, the foldable wing structure comprising: a semi-rigid spar, configured to receive and distribute a first gas; at least two or more inflatable ribs, each inflatable rib being connected to the semi-rigid spar; a plurality of inflatable stringers, wherein each of the plurality of inflatable stringers is connected to at least two ribs, and wherein each of the plurality of inflatable stringers is configured to receive and distribute a second gas to the at least two or more inflatable ribs; a plurality of rigid trailing edge tubes, wherein each of the plurality of rigid trailing edge tubes is attached to at least two inflatable ribs; and an inflatable leading edge apparatus configured to receive the first gas from the semi-rigid spar. When the at least two or more inflatable foldable ribs, the plurality of inflatable stringers, and the inflatable leading edge apparatus are in an un-inflated condition, the foldable wing structure is configured to be folded such that a chord of the foldable wing structure has a length of between approximately 25 percent and 50 percent of a length of a maximum respective chord, and when the at least two or more inflatable foldable ribs, the plurality of inflatable stringers, and the inflatable leading edge apparatus are in an inflated condition, the foldable wing structure is configured to be unfolded such that the length of the chord of the foldable wing structure is approximately equal to the length of the maximum respective chord.

The first gas may comprise a low pressure gas having a pressure at or below 0.1 psi. The second gas may comprise a high pressure gas having a pressure at or above 10 psi. The first gas and the second gas may be generated by a pressure tank, a chemical reaction gas generator, or a propulsion system associated with the very high altitude aircraft. The low pressure gas may comprise atmospheric ram pressure from an air scoop on the aircraft.

According to a fifth aspect, a leading edge segment for use in a foldable wing in a very high altitude aircraft capable of operating at an altitude at or above 85,000 feet is provided, wherein the foldable wing includes a spar that receives and distributes a first gas. The leading edge segment comprises: a semi-rigid shell shaped in a form of a leading edge of the foldable wing, the semi rigid shell being hingedly connected to the spar; a flexible membrane connected to a lowermost portion of the semi-rigid shell and to the spar, thereby forming a chamber within the semi-rigid shell and being configured to accept and retain the first gas; and a passageway between the spar and the semi-rigid shell, wherein the passageway is configured to enable a transfer the first gas from the spar to the chamber.

The first gas may comprise a low pressure gas having a pressure at or below 0.1 psi. The first gas may be generated by a pressure tank, a chemical reaction gas generator, or a propulsion system associated with the very high altitude aircraft.

The leading edge may be configured to be deployed as a result of a high pressure gas inflating at least one bladder between the leading edge and the spar, wherein the high pressure gas has a pressure at or above 10 psi.

According to a sixth aspect of the present invention, a foldable wing for use in a very high altitude aircraft capable of operating at an altitude at or above 85,000 feet is provided. The foldable wing comprises: a first spar section, a second spar section, and a third spar section, wherein the first spar section is positioned closest to a fuselage of the very high altitude aircraft, the second spar section is positioned adjacent to the first spar section, and the third spar section is positioned adjacent to the second spar section, and farthest away from the fuselage; a first hinge and a second hinge, wherein the first hinge rotationally connects the first spar section to the second spar section at a first angle, and wherein the second hinge rotationally connects the second spar section to the third spar section at the first angle, and further wherein the third spar section is configured to rotate about 180° such that an outermost portion of the third spar section is located above an innermost portion of the second spar section, and further wherein the second spar section is configured to rotate about 180° such that an outermost portion of the second spar section is located above an innermost portion of the first spar section, and the outermost portion of the third spar section is located above an outermost portion of the first spar section.

The foldable wing according to the sixth aspect may further comprise at least a fourth spar section and a third hinge, the fourth spar section being configured to rotate about 180° such that an outermost portion of the fourth spar section is located above an innermost portion of the third spar section. The first angle may have a measure of between about 1° and about 4°.

According to a seventh aspect of the present invention, a foldable wing for use in a very high altitude aircraft capable of operating at an altitude at or above 85,000 feet is provided, the foldable wing comprising: a first, second and third spar section, wherein the first spar section is closest to a fuselage of the very high altitude aircraft, the second spar section is adjacent to the first spar section, and the third spar section is adjacent to the second spar section, and farthest away from the fuselage; a first hinge and a second hinge, wherein the second hinge is connected to the second spar section and third spar section at a first angle, and wherein the second hinge is configured to rotate the third spar section about the second spar section at the first angle such that a farthest-most portion of the third spar section is located above an innermost portion of the second spar section, and further wherein the first hinge is connected to the first spar section and the second spar section at the first angle, and wherein the first hinge is configured to rotate the second spar section about the first spar section at the first angle such that a farthest-most portion of the second spar section is located above an innermost portion of the first spar.

According to the seventh aspect, the first angle is between about 1° and about 4°, and wherein additional spar sections and hinges can be added such that each can rotate and fold over an inner adjacent spar section.

According to an eighth aspect of the present invention, a foldable wing for use in a very high altitude aircraft capable of operating at an altitude at or above 85,000 feet is provided. The foldable wing comprises: a pluiality of hinges; a plurality of spar sections, wherein each of the plurality of spar sections is configured to receive and transfer a first gas, and wherein each of the plurality of hinges rotationally connects a respective spar section to an adjacent spar section; and a plurality of inflatable ribs, wherein each of the inflatable ribs includes a rib section, a first arm, and a second arm, and wherein the first arm is positioned adjacent to a respective spar section, and the second arm is positioned adjacent to an adjacent spar section, and wherein the first arm is configured to inflate when the first arm receives the first gas, and the second arm is configured to inflate when the second arm receives the first gas. Upon inflation, the first arm and second arm are further configured to cause the respective spar section and the adjacent spar section to rotate with respect to one another until the respective spar section and the adjacent spar section couple with one another. The rib is configured to inflate until the rib has a substantially perpendicular orientation with respect to the coupled spar sections.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features and advantages of the present invention will best be understood by reference to the detailed description of the preferred embodiments that follows, when read in conjunction with the accompanying drawings, in which:

FIGS. 1A-1F illustrate a very high altitude aircraft with foldable wings according to an embodiment of the present invention.

FIGS. 2A-2C illustrate a foldable wing structure as it unfolds according to an embodiment of the present invention.

FIG. 3 illustrates a folding wing structure according to an embodiment of the present invention.

FIG. 4 illustrates a side view of an inflatable rib for use in a foldable wing in a very high altitude aircraft according to an embodiment of the present invention.

FIGS. 5A and 5B illustrate cross-sectional views of the inflatable rib shown in FIG. 4.

FIG. 6 illustrates a perspective view of a foldable wing and an inflatable rib according to an alternate embodiment of the present invention.

FIG. 7 illustrates a cross-sectional side view of a foldable wing and drooping leading edge structure according to according to an embodiment of the present invention.

FIG. 8 illustrates another cross-sectional view of the inflatable wing shown in FIG. 7 following inflation of the drooping leading edge structure according to an embodiment of the present invention.

FIGS. 9-13 illustrate a sequence of perspective views of a foldable wing structure, as the foldable wing structure folds to a storage position, and wherein foldable wing segments are connected by hinges that are canted at a first angle according to an embodiment of the present invention.

FIGS. 14A-14D illustrate several views of a foldable wing structure wherein foldable wing segments are connected by hinges that are not canted at a first angle.

FIGS. 15A-15G illustrate several views of the foldable wing structure shown in FIGS. 9-13 according to an embodiment of the present invention.

FIGS. 16 and 17 illustrate a foldable rib and spar extending structure according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The various features of the preferred embodiments will now be described with reference to the drawing figures, in which like parts are identified with the same reference characters. The following description of the presently contemplated best mode of practicing the invention is not to be taken in a limiting sense, but is provided merely for the purpose of describing the general principles of the invention.

I. Deployment of Very High Altitude Aircraft

FIGS. 1A-1F illustrate deployment of a very high altitude aircraft (VHA aircraft) 100 according to an embodiment of the present invention. VHA aircraft 100, as shown in FIGS. 1A-1F, can be deployed by various means, including other high altitude operating aircraft (i.e., hypersonic aircraft), rockets and other means. As shown in FIGS. 1A-1F, VHA aircraft 100 is deployed at a very high altitude in a rocket. According to an exemplary embodiment of the present invention, VHA aircraft 100 is stored within fairing 2 of the rocket, at the nose section. Because VHA aircraft 100 is deployed via a rocket, VHA aircraft 100 can be deployed anywhere on the globe within an hour or two from a decision to launch. Such a rapid deployment provides the ability to rapidly acquire pertinent and timely information, in many cases hours, days or weeks before other more conventional information gathering resources, including satellites, can be similarly deployed. According to an embodiment of the present invention, very high altitude comprises altitudes between about 85,000 feet above sea level, and about 150,000 feet above sea level.

FIG. 1E illustrates left wing foldable structure 8 a after all three left wing foldable segments 12 a-c have unfolded and locked together. The unfolding of each left wing foldable structure 12 a-c and locking together of spars 16 will be described in greater detail below. As those of ordinary skill in the art of the present invention can appreciate, there can be one, two, three or more wing foldable segments 12 for VHA aircraft 100. According to a preferred embodiment of the present invention, the number of left wing foldable segments 12, and right wing foldable segments 14 will be equal, though that need not always be the case. Finally, as shown in FIG. 1F, foldable left wing structure 8 a is fully extended and fully inflated. FIGS. 2A-2C illustrate an unfolding of foldable left wing structure 8 a from a different perspective than that shown in FIGS. 1A-1F according to an embodiment of the present invention. In FIGS. 2A-2C, foldable left wing structure 8 a, and in particular first left wing foldable segment 12 a, is shown as it unfolds to an extended state (FIG. 2C). In FIG. 2A, left wing foldable segment 12 a is un-extended (i.e., not inflated); in FIG. 2B, left wing foldable segment 12 a is extended, but not yet completely inflated. Ribs 26 have been inflated, extending wing covering 18 to the full width of foldable left wing structure 8 a, as shown by the direction of arrows B. Foldable left wing structure 8 a now takes a more wing-like shape or form, though it is not yet capable of generating lift, because wing covering 18 has not been pulled taut. Leading edge segment 20 folds up, as arrow A indicates. In FIG. 2C, ribs 26 are completely inflated, creating a definite shape to foldable left wing structure 8 a; stringers 30 are inflated, and cause foldable left wing structure 8 a to expand in the direction of arrows C and D; and trailing edge segments 24 can also be inflated at this time.

FIG. 1E illustrates left wing foldable structure 8 a after all three left wing foldable segments 12 a-c have unfolded and locked together. The unfolding of each left wing foldable structure 12 a-c and locking together of spars 16 will be described in greater detail below. As those of ordinary skill in the art of the present invention can appreciate, there can be one, two, three or more wing foldable segments 12 for VHA aircraft 100. According to a preferred embodiment of the present invention, the number of left wing foldable segments 12, and right wing foldable segments 14 will be equal, though that need not always be the case. Finally, as shown in FIG. 1F, foldable left wing structure 8 a is fully extended and fully inflated. FIGS. 2A-2C illustrate an unfolding of foldable left wing structure 8 a from a different perspective than that shown in FIGS. 1A-1F according to an embodiment of the present invention. In FIGS. 2A-2C, foldable left wing structure 8 a, and in particular first left wing foldable segment 12 a, is shown as it unfolds to an extended state (FIG. 2C). In FIG. 2A, left wing foldable segment 12 a is un-extended (i.e., not inflated); in FIG. 2B, left wing foldable segment 12 a is extended, but not yet completely inflated. Ribs 26 have been inflated, extending wing covering 18 to the full width of foldable left wing structure 8 a, as shown by the direction of arrows B. Foldable left wing structure 8 a now takes a more wing-like shape or form, though it is not yet capable of generating lift, because wing covering 18 has not been pulled taut. Leading edge segment 20 folds up, as arrow A indicates. In FIG. 2C, ribs 26 are completely inflated, creating a definite shape to foldable left wing structure 8 a; stringers 22 are inflated, and cause foldable left wing structure 8 a to expand in the direction of arrows C and D; and trailing edge segments 24 can also be inflated at this time.

According to a preferred embodiment of the present invention, when ribs 26, stringers 30, and leading edge segment 20 are in an un-inflated condition, foldable wing structure 12 is configured to be folded such that a width of foldable wing structure 12 is between approximately 25 percent and 50 percent of a maximum chord width.

According to a preferred embodiment of the present invention, when ribs 26, stringers 30, and leading edge segment 20 are in an inflated condition, foldable wing structure 12 is configured to be unfolded such that the width of foldable wing structure 12 is approximately equal to the maximum chord width.

According to a preferred embodiment of the present invention, when ribs 26, stringers 26, and leading edge segment are in an inflated condition, foldable wing structure 12 is configured to be unfolded such that the width of foldable wing structure 12 is approximately equal to the maximum chord width.

FIG. 3 illustrates a front perspective view of left wing foldable segment 12 showing flow of high pressure gas and low pressure gas within at least one inflatable wing structure. According to a preferred embodiment of the present invention, low pressure gases range in value of psi at or below 1 psi, and high pressure gases range in psi values from about 10 psi to about 100 psi. According to a preferred embodiment of the present invention, each left wing foldable segment 12 a comprises at least one inflatable rib 26, and preferably at least two: one in the middle of left wing foldable segment 12 and another at the edge that forms the hinge point with an adjacent left wing foldable segment 12. Of course, as those of ordinary skill in the art can appreciate, the number of ribs 26 depends on a variety of factors, and thus the embodiments of the present invention are not to be construed as limited to left wing foldable segment 12 with one, two, or only three ribs 26. As FIGS. 3 and 4 illustrate, each left wing foldable segment 12 comprises folding leading edge 20, spar 16, stringers 30, ribs 26, inflatable joints 36, and composite trailing edge with inflatable joints 38. According to a preferred embodiment of the present invention, spar 16 can be fabricated from a composite material, though this need not be the case. Other materials can be used to make spar 16 rigid, including titanium, aluminum, plastic, and other materials. According to still a further exemplary embodiment of the present invention, spar 16 can also be made inflatable (i.e., a prism inflatable structure or substantially uniform polyhedron structure).

II. Inflatable Ribs with Inflatable or Rigid Stringers and Trailing Edge

According to a preferred embodiment of the present invention, there is a rib 26 at each hinge point in left wing foldable segment 12. As discussed briefly above, one or more ribs 26 can be located within each left wing foldable segment 12 between hinge points. According to a first preferred embodiment of the present invention, a first configuration of rib 26 comprises a plurality of linked, circular cross section tubes 40. According to a preferred embodiment of the present invention, use of linked, circular cross-section tubes 40 allows rib 26 to be made in any airfoil shape required. FIG. 4 illustrates a side view of rib 26 according to an embodiment of the present invention. Rib 26 is made up of a plurality of tubes, 40 a-40 d, that are substantially circular (though they need not be, as one of ordinary skill in the art of the present invention can appreciate), and are interconnected, at one or more locations, by tube link 44. In the embodiment shown in FIGS. 4, 5A, and 5B, there is only one tube link 44, so that the drawing is not cluttered; according to an exemplary embodiment of the present invention, there can be several tube links 44 so that the gas that is input to tubes 40 of rib 26 can more easily flow to the other tubes 40. Between each tube 40, there is tube connecting area 42 (e.g., 42 a, 42 b, 42 c, 42 d), which is a flat piece of material to connect tubes 40 together, and to help provide a definite shape to rib 26. A rib 26 that is formed in this manner may be created from a mold wherein, for example, molten plastic under high pressure is forced into a die creating the inflatable structure. Alternatively, the rib may be created by appropriately sewing plastic impregnated cloth sheets. Such means for manufacturing inflatable devices are well known, and shall not be discussed further, for purposes of brevity and clarity. As shown in FIG. 5B (which corresponds to a view of rib 26 at line 5B-5B, of FIG. 4), there are no tube links 44, because at that location, and others similarly situated, only tube connecting area 44 exists between tubes 40.

According to another exemplary embodiment of the present invention, rib 26 can be manufactured from one circular cross section tube, as shown in FIG. 6, where the tube is specifically woven to have the proper airfoil shape in the side view, both for thickness and camber. For example, rib 26 can be made of a material, such as Vectran fiber, that can be braided around a rigid mandrel of the proper shape, and consist of fiber orientations to maintain that shape when inflated.

According to another exemplary embodiment of the present invention, rib 16 can be manufactured from one circular cross section tube, as shown in FIG. 6, where the tube is specifically woven to have the proper airfoil shape in the side view, both for thickness and camber. For example, rib 16 can be made of a material, such as Vectran fiber, that can be braided around a rigid mandrel of the proper shape, and consist of fiber orientations to maintain that shape when inflated.

The number and location of stringers 30 is selected to give good control of the airfoil shape of the deployed wing. The wing aft of spar 16 is covered with flexible membrane skin 46, similar to the cloth that covered aircraft wings. According to a preferred embodiment of the present invention, the pressure in the inflated ribs provides the force to tension the flexible membrane skin 46, as shown in FIG. 6.

According to a preferred embodiment of the present invention, ribs 26 are inflated with high pressure gas 32, as shown in FIG. 3, as are stringers 30. Low pressure gas 34 is input to spars 16, which is then used to inflate folding leading edge 20, as discussed in greater detail below. Both high pressure gas 32 and low pressure gas 34 can come from a pressure tank (not shown), from a chemical reaction gas generator (also not shown), or from the exhaust of the propulsion engine.

FIGS. 7 and 8 illustrate operation of foldable leading edge 20 according to an embodiment of the present invention. While the previously described folding system allows a large wing to be folded into a small volume, in some cases, even greater compaction is needed. In this case, the wing leading edge could be made to fold also. The aerodynamically critical foldable leading edge 20 comprises two components: folding leading edge shell 50 and leading edge flexible membrane 28. Folding leading edge shell 50 can be made of an appropriately molded composite shell part. Alternatively, leading edge shell 50 can be made from known metals or alloys. Leading edge shell 50 continues around the leading edge onto the front lower surface of foldable wing structure 8. However, leading edge shell 50 of foldable leading edge 20 stops well in front of the lower front face of spar 16, and the gap is bridged by leading edge flexible membrane 28. Leading edge shell 50 is attached to the upper front corner of spar 16 with hinge 52 that allows leading edge shell 50 to fold downwards. Leading edge flexible membrane 28 is large enough that leading edge shell 50 can fold entirely under spar 16, greatly decreasing the volume of foldable wing structure 8.

III. Drooping Semi-Rigid Leading Edge

Referring to FIGS. 3 and 7, low pressure gas 34 is received into spar 16 from fuselage 10. A plurality of spar air holes 48 exhaust low pressure gas 34 into folding leading edge 20. As shown in FIG. 7, leading edge shell 50 hangs downward, relative to wing foldable segment 12, from hinge 52. Hinge 52, as those of ordinary skill in the art of the present invention can appreciate, can be a true hinge (i.e., interlocking cylindrical members with a center pin), or can be a simple piece of flexible material acting as a hinge. As low pressure gas fills spar 16, it begins to exit spar 16 via spar air holes 48 into an interior section or chamber 51 of leading edge shell 50. Chamber 51 is created by the interior portion of leading edge shell 50, and membrane 28. Low pressure gas 34 fills chamber 51, and causes membrane 28 to pull taut, as shown in FIG. 8. Once chamber 51 is completely filled, leading edge segment 20 is fully formed and joined with the balance of foldable wing segment 8 to form an effective airfoil. As an alternative method, higher pressure gas may be used to inflate some number of bladders or air bags within the leading edge to provide the deployment force.

Referring to FIG. 3, low pressure gas 34 is received into spar 16 from fuselage 10. A plurality of spar air holes 48 exhaust low pressure gas 34 into folding leading edge 20. As shown in FIG. 7, leading edge shell 50 hangs downward, relative to wing foldable segment 12, from hinge 52. Hinge 52, as those of ordinary skill in the art of the present invention can appreciate, can be a true hinge (i.e., interlocking cylindrical members with a center pin), or can be a simple piece of flexible material acting as a hinge. As low pressure gas fills spar 16, it begins to exit spar 16 via spar air holes 48 into an interior section or chamber 51 of leading edge shell 50. Chamber 51 is created by the interior portion of leading edge shell 50, and membrane 28. Low pressure gas 34 fills chamber 51, and causes membrane 28 to pull taut, as shown in FIG. 8. Once chamber 51 is completely filled, leading edge segment 20 is fully formed and joined with the balance of wing foldable wing segment 8 to form an effective airfoil. As an alternative method, higher pressure gas may be used to inflate some number of bladders or air bags within the leading edge to provide the deployment force.

According to an exemplary embodiment of the present invention, foldable wing structure 8 can be folded in a spiral configuration, as shown and described in reference to FIGS. 9-13, and 15. According to a preferred embodiment of the present invention, several features are preferably present in order to spirally fold foldable wing structure 8: foldable wing structure 8 preferably has at least three wing foldable segments 12, preferably four: e.g., 12 a, 12 b, 12 c, 12 d; each foldable wing segment 12 preferably contains a spar 16 to carry the major loads; substantially the entire airfoil aft of spars 16 comprises a combination of collapsible, inflatable, and flexible elements, such that substantially the entire airfoil aft of spar 16 can be substantially collapsed and stowed in the aft part of spar 16 of each foldable wing segment 12; and at the junction of spars 16, there is hinge 54 (e.g., 54 a, 54 b, 54 c, 54 d) with an axis of rotation that is approximately, but not exactly, perpendicular to the plane of foldable wing structure 8.

IV. Spiral Fold Spar

FIGS. 14A-C illustrate a hypothetical wing structure in which a hinge is provided that is substantially perpendicular to the plane of the wing. The purpose of FIGS. 14A-C is to illustrate why spiral wing hinge 54 needs to be at an angle other than substantially perpendicular to the plane of foldable wing structure 8. As shown in FIG. 14A, the hypothetical wing comprises two segments, A and B; each are joined together by hinge g, which is substantially perpendicular to plane P of the hypothetical wing. FIG. 14B illustrates what happens when segments A and B are folded together: they are nearly perfectly aligned—point d of segment B is adjacent to point c of segment A. FIG. 14C illustrates the substantially perpendicularity of hinge g. In contrast, according to a preferred embodiment of the present invention, spiral foldable wing structure 12 comprises spiral wing hinge 54 that is offset from perpendicular as shown in FIG. 15. In FIGS. 15A-15G, simplified diagrams of foldable wing segments 12 a and 12 b are shown to illustrate the embodiments of the present invention. In FIG. 15A, foldable wing segment 12 a is rotationally hingedly connected via hinge 54 to foldable wing segment 12 b. The angle of offset θ is shown to be about 4.7° (i.e., an angle of offset from perpendicular). The angle of offset θ can be between 1 and 5° according to a preferred embodiment of the present invention. In FIG. 15B, foldable wing segment 12 b has been rotated about hinge 54; because the angle of offset θ was set to 94.7° in the direction shown, foldable wing segment 12 b folded under foldable wing segment 12 a. FIG. 15C is a perspective view of foldable wing segments 12 a and 12 b, and FIGS. 15D-15G illustrate the spatial relationship between foldable wing segments 12 a and 12 b as foldable wing segment 12 b is rotated through about 180° with respect to foldable wing segment 12 a.

FIGS. 14A-C illustrate a hypothetical wing structure in which a hinge is provided that is substantially perpendicular to the plane of the wing. The purpose of FIGS. 14A-C is to illustrate why spiral wing hinge 54 needs to be at an angle other than substantially perpendicular to the plane of foldable wing structure 8. As shown in FIG. 14A, the hypothetical wing comprises two segments, A and B; each are joined together by hinge g, which is substantially perpendicular to plane P of the hypothetical wing. FIG. 14B illustrates what happens when segments A and B are folded together: they are nearly perfectly aligned—point d of segment B is adjacent to point C of segment A. FIG. 14C illustrates the substantially perpendicularity of hinge g. In contrast, according to a preferred embodiment of the present invention, spiral foldable wing structure 12 comprises spiral wing hinge 54 that is offset from perpendicular as shown in FIG. 15. In FIGS. 15A-15G, a simplified diagram of foldable wing segments 12 a and 12 b are shown to illustrate the embodiments of the present invention. In FIG. 15A, foldable wing segment 12 a is rotationally hingedly connected via hinge 54 to foldable wing segment 12 b. The angle of offset θ is shown to be about 4.7° (i.e., an angle of offset from perpendicular). The angle of offset θ can be between 1 and 5° according to a preferred embodiment of the present invention. In FIG. 15B, foldable wing segment 12 b has been rotated about hinge 54; because the angle of offset θ was set to 94.7° in the direction shown, foldable wing segment 12 b folded under foldable wing segment 12 a. FIG. 15C is a perspective view of foldable wing segments 12 a and 12 b, and FIGS. 15D-15G illustrate the spatial relationship between foldable wing segments 12 a and 12 b as foldable wing segment 12 b is rotated through about 180° with respect to foldable wing segment 12 a.

If spiral wing hinge 54 includes an angle of offset θ, then the end portion of foldable wing segment 12 a, when folded back at about 180°, will lie partially on top of, or below, the end portion of foldable wing segment 12 a (as shown and described in FIGS. 9-13). According to a preferred embodiment of the present invention, angle of offset θ is between about 1° and about 4°.

Because spiral wing hinge 54 is attached to spar 16 with an angle of offset θ, the hinge line is canted slightly in a front (or rear) view, such that spars 16 of respective inboard and outboard foldable wing segments 12 a-d are not parallel to each other, but instead, according to a preferred embodiment of the present invention, the end of the outboard foldable wing segment 12 d is displaced upwards or downwards compared to the end of the inboard foldable wing segment 12 a by approximately the thickness of spar 16. The angle of offset θ is chosen so that the end of the next segment 12 can lie entirely above the previous one; that is, spiral wing hinge 54 a is offset so that the tip of wing foldable segment 12 d lies above the root of wing foldable segment 12 c when folded, thus allowing wing foldable segment 12 c to be entirely above wing foldable segment 12 b, and so on.

According to an exemplary embodiment of the present invention, use of angle of offset θ with spiral wing hinge 54 allows the additional foldable wing segments 12 b-d to be folded such that a third foldable wings segment 12 c from the wing root will lie entirely above first foldable wing segment 12 a from the wing root. If there is a fourth foldable wing segment 12 d, it will lie above second foldable wing segment 12 b.

According to a preferred embodiment of the present invention, a deployment method is provided that substantially minimizes the peak deployment load for deploying foldable wing structure 8. According to the method of deployment, the first step comprises unfolding spiral wing hinge 54 d (shown in FIG. 13) located between the side of fuselage 10 and first foldable wing segment 12 a. Spiral wing hinge 54 d joins foldable wing structure 8 to short wing segment 12 x (which is not foldable, but considered a wing segment for purposes of our discussion), at first foldable wing segment 12 a. Arrow A indicates how foldable wing structure 8 is attached to wing structure 12 x and fuselage 10. Once first foldable wing segment 12 a is deployed, as shown in FIG. 13 (note that when first foldable wing segment 12 a is deployed away from fuselage 10, foldable wing segments 12 b-d are still folded and undeployed, resting upon first foldable wing segment 12 a), then spiral wing hinge 54 c is deployed, wherein spiral wing hinge 54 c (shown in FIG. 13), located between first foldable wing segment 12 a and second foldable wing segment 12 b is rotated, thereby deploying second foldable wing segment 12 b, resulting in foldable wing structure 8 as shown in FIG. 12.

Following deployment of second foldable wing segment 12 b about spiral wing hinge 54 c, third foldable wing segment 12 c can be deployed by rotating it about spiral wing hinge 54 b, as shown in FIG. 12. According to an exemplary embodiment of the present invention, each foldable wing segment 12 rotates clockwise when viewed from above and facing fore of the aircraft. After third foldable wing segment 12 c rotates about spiral wing hinge 54 b, a foldable wing structure 8 appears as shown in FIG. 11. The final rotation of foldable wing segment 12 d then occurs about spiral wing hinge 54 a (shown in FIG. 11), resulting in the foldable wing structure 8 as shown in FIG. 10. Note in FIGS. 10-13, the location of wingtip 56; if a plot were to be made of the position of wingtip 56 in regard to a plane of foldable wing structure 8, the plot of the position of wingtip 56 would rotate and spiral inward and upward in regard to the root of foldable wing structure 8.

Following complete spiral deployment of foldable wing segments 12 a-d, the aft trailing edge portion 24 of foldable wing structure 8 is deployed, as shown in FIG. 9. According to an exemplary embodiment of the present invention, deployment of left and right foldable wing structures 8 a, 8 b can occur simultaneously, or one after the other. According to a preferred embodiment of the present invention, the aforementioned and detailed discussion of method of spiral deployment of foldable wing structure 8 provides a method of foldable wing deployment wherein the longest moment arm during a deployment is the length of one foldable wing segment 12.

V. Pneumatic Deployment of Foldable Wing Structure Via Inflatable Ribs

Referring to FIG. 16, inflatable spar extending rib 58 is shown with spars 16 a, 16 b in a deflated state. Hinge 52 connects spar 16 a and 16 b together, and membrane 46 provides a sealed path for low pressure gas 34 to travel. Spar gas hole 48 passes low pressure gas 34 from spars 16 a, 16 b into inflatable spar extending rib 58. In the deflated state, inflatable spar extending rib 58 folds neatly between spars 16 a, 16 b. Adjacent to spar 16 a is right arm 60 a of inflatable spar extending rib 58 and adjacent to spar 16 b is left arm 60 b of inflatable spar extending rib 58. As low pressure gas begins to fill inflatable spar extending rib 58, both arms 60 a, 60 b fill with low pressure gas 34 as well, extending in both directions, respectively, thereby pushing on spars 16 a, 16 b in the direction of each other. The low gas pressure gives a positive deployment moment for the full 180 degrees of hinge 52 travel. According to another alternate embodiment of the present invention, arms 60 a, 60 b can even be woven as part of spars 16. The gas to inflate the spar tubes and ribs can come from a pressure tank, from a chemical reaction gas generator, or from the exhaust of the propulsion engine.

Following complete inflation of inflatable spar extending rib 58, the configuration of spars 16 a, 16 b and inflatable spar extending rib 58 as shown in FIG. 17. As can be seen, right arm 60 a still pushes against and is adjacent to spar 16 a, while left arm 60 b pushes against and is adjacent to spar 16 b. The main body of inflatable spar extending rib 58 extends backwards, aft of spars 16 a, 16 b to ensure deployment of stringers 30 and trailing edge 38 components, as discussed in detail above.

Following complete inflation of inflatable spar extending rib 58, the configuration of spars 16 a, b and inflatable spar extending rib 58 as shown in FIG. 17. As can be seen, right arm 60 a still pushes against and is adjacent to spar 16 a, while left arm 60 b pushes against and is adjacent to spar 16 b. The main body of inflatable spar extending rib 58 extends backwards, aft of spars 16 a, b to ensure deployment of stringers 30 and trailing edge 38 components, as discussed in detail above.

According to an alternate embodiment of the present invention, hinges 52 in spar 16 can be deployed by any of several exemplary options, such as a motor and gear train at each hinge, or a tensioned wire or cable in the wing leading edge.

The present invention has been described with reference to certain exemplary embodiments thereof. However, it will be readily apparent to those skilled in the art that it is possible to embody the invention in specific forms other than those of the exemplary embodiments described above. This may be done without departing from the spirit and scope of the invention. The exemplary embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is defined by the appended claims and their equivalents, rather than by the preceding description.

All United States patents and applications, foreign patents, and publications discussed above are hereby incorporated herein by reference in their entireties. 

What is claimed is:
 1. A foldable wing for use in a very high altitude aircraft capable of operating at an altitude at or above 85,000 feet, the foldable wing comprising: a first spar section, a second spar section, and a third spar section, wherein the first spar section is positioned closest to a fuselage of the very high altitude aircraft, the second spar section is positioned adjacent to the first spar section, and the third spar section is positioned adjacent to the second spar section and farthest away from the fuselage; a first hinge and a second hinge, wherein the first hinge rotationally connects the first spar section to the second spar section at a first angle, and wherein the second hinge rotationally connects the second spar section to the third spar section at the first angle, and further wherein the third spar section is configured to rotate about 180° such that an outermost portion of the third spar section is located above an innermost portion of the second spar section, and further wherein the second spar section is configured to rotate about 180° such that an outermost portion of the second spar section is located above an innermost portion of the first spar section, and the outermost portion of the third spar section is located above an outermost portion of the first spar section.
 2. The foldable wing according to claim 1, further comprising at least a fourth spar section and a third hinge, the fourth spar section being configured to rotate about 180° such that an outermost portion of the fourth spar section is located above an innermost portion of the third spar section.
 3. The foldable wing according to claim 1, wherein the first angle has a measure of between about 1° and about 4°. 